The invention relates to optical correlation techniques for characterizing materials and optical waveforms.
Modern laser technology permits the routine generation of ultrashort optical pulses, i.e., pulses having a duration of less than about 1 psec. Some lasers can even generate pulses as short as about 10 fsec. More generally, modern laser systems can produce ultrafast optical waveforms that have features as short as ultrafast pulses, e.g., a terahertz train of ultrashort pulses. See, e.g., U.S. Pat. Nos. 5,682,262 and 5,719,650. Such ultrashort waveforms (including single pulse waveforms) can be used to probe chemical and physical phenomena in atoms, molecules, and materials. Unfortunately, the time scales for such measurements and for the optical waveforms themselves exceed the bandwidth of most, if not all, electronic detectors. As a result, many measurements involve optical correlation techniques in which two or more waveforms overlap on a sample or non-linear optical crystal.